This invention relates to vehicle suspensions and, more particularly, relates to pneumatic and rubber-pneumatic vehicle suspension systems.
Suspensions are essential elements in the structure of vehicles, such as heavy vehicles having tandem axles, and articulation of conventional suspensions often is limited and will not permit off-highway travel. Road travel of vehicles having such suspensions often is uncomfortable with poor road-holding characteristics when the vehicle is unloaded. Conversely, stability of the vehicle may suffer during full load conditions and during tilting of the vehicle beds during unloading such as by dumping, due to inherent instability with high centers of gravity.
Road shock under fully loaded and unloaded conditions usually is transmitted to the vehicle frame due to the lack of adequate cushion. Severe wear of the vehicle or damage to goods transported thus often results over rough road conditions, especially at high speeds.
U.S. Pat. No. 2,902,291 discloses a pneumatic suspension system for vehicles in which four bellows units positioned one on each side of a chassis forwardly and rearwardly of a single axle assembly obviate the need for torque rods and tubes. A longitudinally extending hollow member serves as a support and an air storage space for each pair of bellows units on a side of the vehicle, the said hollow member having a central partition to form two independent air reservoirs. Shock absorbers are required to damp oscillations of the vehicle. U.S. Pat. No. 2,896,964 discloses a combination of air and steel springs in which two different sets of air springs are provided. One set of springs is under constant load while another set is so arranged that it is actuated only when the first set is partially compressed such as, for example, when sway of the vehicle begins to occur.
Distortion of vehicle frames due to travel of single axle and tandem axle suspensions over uneven roadbeds often results in twisting of the frames with attendant transitional misalignment and "steering" of the axles.
It is a principal object of the present invention to provide an improved air suspension, preferably an air-rubber suspension, which effectively cushions road shock and vibration of a vehicle under all load conditions to improve the vehicle ride.
Another object of the invention is to provide an improved suspension which is self-damping under all load conditions to obviate the need for conventional shock absorbers, thus simplifying maintenance and repair.
A further object of the present invention is the provision of a suspension which allows substantially unlimited articulation of a tandem axle system. A torsionally-stiff cross member is provided to impart to the vehicle frame for improved axle alignment.